Galvanized "Tin" Kitchen Countertops

A. Hi. The zinc countertops of the old days, and of higher end kitchens today, are solid Zinc sheet for countertops, etc. [affil links], not galvanized. Galvanized sheet metal has a thin coating of zinc on steel sheet.

Unfortunately, there isn't much leeway either to patina or repair the thin galvanized layer as opposed to a solid sheet. But there are patinas for zinc that you could try.

Clearcoats may not stick. But I guess trying to clearcoat it is the best approach anyway. Good luck.

Regards,

A. Perhaps dilute acetic acid (vinegar) would clean the hot dip galvanizing coating. From the photos the water could be "hard" or perhaps the soap is particularly prone to form a lot of "scum." At my home with very "hard" water we use a liquid baby soap and the sinks stay a lot cleaner. You cannot use many "hard" water cleaners because they contain the strong acid, Hydrochloric Acid, (HCl) and they will dissolve the zinc coating.
Regards,

A. Hi Sylvia. As Dr. Cook says, a portion of the zinc coating can probably dissolve in cleaners that are made to remove calcium deposits like Lime Away [on eBay or Amazon] or C-L-R [on eBay or Amazon] , but they may be pretty much necessary. Also I don't think I'd try to read into Dr. Cook's reply any implication that full strength vinegar is harmless to the galvanized coating. So I think it would be a matter of trying careful timing followed by neutralization with baking soda.

Compounding the problem is that, unfortunately, what people perceive as a calcium buildup is not always a calcium buildup -- sometimes it's corrosion products of the zinc. You can (maybe) remove the corrosion byproducts the same way you remove calcium buildups, but you can't repair the corrosion.

I don't like saying much in the possible event of contract disputes, but I would not want to use galvanized metal as a sink surface in general unless the owner accepted the dull old country farmhouse look, rather than a clean sparkly look -- because galvanizing is not a decorative finish, it is a functional finish. It happens to be shiny when new but is not intended to retain the shine at all; galvanizing is just not the same thing as a decorative finish like nickel plating, chrome plating or lacquered brass plating. While your agency restrooms may be upscale from roadside restrooms, I've been to enough public restrooms to know that unlike private bathrooms, water will constantly be splashed all over the countertops, never wiped dry by the user, and they'll constantly be left a wet, sloppy mess. As a matter of personal opinion I don't think galvanized metal is appropriate for a public restroom.

Regards,

A. What you see in the photo and in your country home is what galvanized steel naturally does over time; the zinc oxide surfaces protect the ferrous metal below the zinc layer. You cannot really stop or remove the layer you will simply continue to alter it's appearance temporarily. Naptha or turpentine [on eBay or Amazon] will affect a change in the surface appearance, however, it will not 'remove' the layer you find offensive.

Best,

A. Hi Beverly. This is the zinc surface very slowly wearing away and corroding away over time. Microscopically fine metal powders usually appear to be black rather than metal colored or white because their shapes tend to not reflect any light. Zinc is an essential nutrient rather than a toxin (one multivitamin claims it has "everything from A to Zinc") so I wouldn't be concerned about such tiny quantities. But you could see if a [on eBay or Amazon] with diluted vinegar can stop the black for a week or two.

Regards,

A. Hi, Sarah. I'd say it's reasonably likely that what you are thinking of is NOT food-safe. But the confusion comes from the fact that people use the word 'tin' in a colloquial fashion that has nothing to do with its real definition :-)

Tin [link is to Wikipedia] is a metallic element, one of the 94 naturally occurring elements. The element tin is food-safe. In fact, for years, foods cans were tin plated, and tin is one of few metals that is not regulated in water and wastewater.

If what you have in mind were actually pure tin metal, it would be food-safe.

But people also use the word "tin" as shorthand for "sheet metal"; the sheet metal is rarely actually tin, it is usually steel, and the coating on it, probably zinc, may not be food safe.

Galvanized sheet metal, which is what I suspect you are actually thinking of, is steel that has been zinc (not tin) coated by dipping into a vat of molten zinc. Although zinc is generally "safe" (it's an essential nutrient, not a toxin), it's not considered "food-safe" because it dissolves in acidic foods too readily. Also the zinc is very prone to white corrosion staining, and to deter that, it is often dipped in chromate. Chromate is NOT food-safe.

I think the right rule of thumb is if the metal was intended to be used as a countertop it is safe, if it was not made for that purpose it is not safe to use it as a food surface.

Contact cement will probably work for fastening it to the plywood. The only good way to join pieces is probably a rolled seam:

A. I have had galvanized countertops in the kitchen of our ranch house for 6 years. I like the look and have found them to be maintenance free. I never have prepared food directly on the countertop so I haven't had a problem there, but many foods, especially foods high in acidity, will discolor the tin [Ed. note: actually it's "zinc" not tin.]. The discoloration can be unsightly.

A. Nothing is forever, Paddie, but the purpose of the zinc coating is to deter the underlying sheet metal from rusting, so, yes, it sounds okay to me. Galvanized sheet metal is most resistant to rust when it is out in the open so it can "breathe" -- carbon dioxide in the air very slowly reacting with the zinc surface to form a hard, glassy, zinc carbonate surface.

A. Hi Sue. Tin is 100% food-safe, but if you keep calling steel sheet metal that is galvanized with zinc "tin", it will remain hard to get a clear answer :-)

Odds are 100:1 that you mean galvanized steel sheet metal.

Zinc is not a toxin, it's an essential nutrient, but it dissolves too readily in acidic foods, leading to potential over consumption, to be considered food safe. Further, it may have received a final dip in chromate (hexavalent chrome), which is certainly not food safe. In my own personal assessment it's not likely to be a serious hazard, but we live in a squeamish age, and I can't recommend galvanized sheet steel for food service countertops.

Paint and clearcoats stick very poorly to galvanized metal, so I don't like that answer either. Getting proper adhesion involves pretreatments that would cause the galvanizing to lose any decorative value :-(

Regards,

A. I HAVE JUST INSTALLED GALVANIZED COUNTERTOPS IN MY KITCHEN.
I HAVE SOME "SPOTS" FROM SOAPS OR ACIDS I SUPPOSE, BUT THE LOOK FOR MY RANCH KITCHEN IS A GOOD ONE. I HAVE 6 INCH BACKSPLASH AND VENT HOOD IN THE SAME MATERIAL. MY DISSATISFACTION WAS THAT THEY WERE TOO SHINY AT FIRST BUT THEY ARE DULLING WITH TIME. AS FAR AS FOOD SAFETY ... WHO PUTS THEIR FOOD DIRECTLY ON THE COUNTERTOP?
MY IDEA WAS FOR THE TOPS TO AGE AND THEN I WANT TO BUFF AND SEAL THEM. I HAD READ IN THIS COLUMN ABOUT SOMEONE USING PASTE WAX. I SAW A TABLE WITH THE SAME TOP THAT HAD BEEN STAINED, DISTRESSED, AND THEN SEALED AND IT WAS A GOOD LOOK. AT ITS WORST I LIKE IT MORE THAN GRANITE WHICH HAS BECOME AS COMMON AS FORMICA. AND SURELY THERE WILL BE A SHORTAGE SOON BECAUSE EVERYONE IS USING IT.
I WOULD LOVE ANY TIPS ON FINISHING THE GALVANIZED TIN.

A. Hi Margie. 5% phosphoric acid is used to remove the white rust (assuming yet again that you mean zinc galvanized steel sheet metal rather than actual tin). My assumption is that diluted vinegar could be substituted with passable results. Good luck.

Regards,

A. Hi Marie. Yes, people call sheet metal "tin", but slang means whatever people want it to mean, so we can't put a fine point on it and say whether it implies or doesn't imply that the steel sheet has a galvanized zinc coating. BTW, I don't think that "galvanized aluminum" , i.e., aluminum dipped in molten zinc, exists. But the store may sell plain aluminum sheet. A magnet should tell you whether it's aluminum sheet (non-magnetic) vs. galvanized steel sheet.

I think contact cement will work.

Regards,

A. Hi Marisa. Hundreds of millions of people, maybe even you, have been cooking in aluminum pots and pans for their whole lives. So, as a countertop material, aluminum doesn't concern me in the least.

But since you liked this thread you may also like Letter 22551 "Is There a Danger in Cast Aluminum Cookware?" and Letter 12362, "Coating tables and bar tops with thick clear pourable plastic".

Regards,

You are a knight in shining armor! Thank you so much for the info/link. AND for answering me period, much less same day! Your patience with people is amazing. You should be awarded for answering redundant questions with such patience. Thank you again!

Thanks for the kind thoughts, Marisa. I have the world's best job, so I do try to be patient enough to not blow this gig :-)

(Response time is just luck of the draw. I check for new e-mail every few hours and have no choice but to do "last in / first out" because I can't get them all done and would otherwise just get further & further behind every day).

Regards,